RE: Linux Kernel Summit
From: Peter Vogel <pvogel_at_arsin.com>
Date: 2001-04-03 22:55:43 CEST
I agree with Jason. I too have managed large, long-lived
That said, I'd be willing to settle for those features
-- Peter A. Vogel Manager, Configuration Management Arsin Corporation 4800 Great America Parkway Suite 425, Santa Clara, CA 95054 > -----Original Message----- > From: Jason Molenda [mailto:firstname.lastname@example.org] > Sent: Tuesday, April 03, 2001 1:47 PM > To: email@example.com > Cc: firstname.lastname@example.org > Subject: Re: Linux Kernel Summit > > > Jim Blandy wrote: > > > I don't think Subversion should be involved in: > > 1) checking that bits were transmitted across the > network without > > corruption, or > > 2) checking that bits were stored on disk without corruption. > > > I've worked with three large (multi-gigabyte), long-lived (5-10 > years of history) cvs repositories, and each of them had file > corruption problems. Some problems were due to OS/filesystem > problems (most notably NFS). Some problems seem to have been RCS > bugs (file truncation - probably a disk filled and RCS didn't do > the right thing). Some seem to have been cvs bugs (I'm not even > sure how those files got in that state). Every large repository > I've worked with has accumulated a few dozen of these. > > It doesn't do me any good if I have backups -- in every case, I didn't > find the corruption until many months after the fact. The corrupted > revisions were often some of the oldest, so the only time we'd find it > is if a user ran a command like "cvs log" (which digs through all the > revisions) on the corrupt file. > > My desire for a checksum is obvious: I want to (a) know if a file > is corrupt, and (b) I want to find the corruption reasonably close > to the time when it happens. Backups, RAIDs, etc., are all nice, > but they don't do me any good if a repository is silently corrupted > over time. With CVS, I'm reduced to stupid things like running rcs > over every file in my repository to check file integrity. > > Assuming that the OS will never corrupt a file is not good enough; > some OS somewhere at some time is going to corrupt one. And if > subversion doesn't have a way to detect that corruption, people > are going to blame it on svn. Or the problem could happen at a > higher level - maybe the svn filesystem or database could corrupt > part of a file's revisions. As you offer plug-in-able databases, > you'll be opening yourself up to even more points of failure. > > The sine qua non of a revision control system is that your sources > are never corrupted. If there is disagreement about the utility > of these sorts of integrity checks, make them an optional setting. > I wager that many administrators will enable these checks even if > they incur a non-trivial performance penalty in the process. CPU > is cheap; my time doing detective work trying to track down corrupt > revision history is expensive. > > (Of course you don't see me implementing anything, so I expect my > opinion to be given the appropriate weighting. But I thought I'd > throw in my two cents) > > Jason >Received on Sat Oct 21 14:36:27 2006
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